What's James McAvoy's most iconic role?

James McAvoy's most iconic role is widely considered to be Charles Xavier (Professor X) in the X-Men prequel film series, beginning with X-Men: First Class in 2011. He brought a younger, more vulnerable version of the character to life across multiple films, earning widespread praise for his chemistry with Michael Fassbender and his emotional depth in the role. Some also point to his performance in Split (2016) and its sequel Glass as career-defining work, where he played a man with 24 distinct personalities, showcasing his extraordinary range. That performance earned him significant critical acclaim and demonstrated his ability to carry a film with a physically and psychologically demanding role.